Vapor electric apparatus.



P. H. THOMAS.

VAPOR ELECTRIC APPARATUS.

APPLICATION FILED SEPT-12. 1912.

Patented Feb. 6, 1917.

URRENT WITNESSES PERCY H. THOMAS, 015 UPPER MONTCLAIR, NEW JERSEY, ASSIGNOR TO COOPER HEWITT ELECTRIC COMPANY, OF HOBOKEN, NEW JERSEY, A CORPORATION OF NEW JERSEY.

VAPOR ELECTRIC APPARATUS.

Specification of Letters Patent.

Patented Feb. 6, 1917.

To all whom it may concem:

Be it known that I, PERCY H. THOMAS, a citizen of the United States, and resident of Upper Montclair, county of Essex, State of New Jersey, have invented certain new and useful Improvements in Vapor Electric Apparatus, of which the following is a specification.

My invention relates to the operation of mercury vapor devices, more particularly when run under high pressure, in constant current circuits. Constant current circuits are utilized frequently and without difliculty 1n connection with consumption devices characterized" by an absorption of voltage which increases only with rising current. When the serially operated device is, however, such that the voltage may rise without an increase in current, simple series operation has the tendency to be unstable as will hereinafter be explained more particularly.

The object of the present invention is to secure a type of series circuit or designs of mercury vapor device such as can be successfully operated on a constant current circuit.

The particular systems made use of will be explained more fully in connection with the several figures of the drawings, in which Figure 1 illustrates a constant current circuit feeding mercury vapor apparatus; and Fig. 2 shows another such system adapted to alternating or direct current. Fig. 3 shows a specially formed lamp adapted to this service; and Figs. 4 and-5 show characteristic voltage-current curves.

In Fig. 5 I show a characteristic curve representing a device having a voltage current relation which requires no correction for series operation. It will be noted from this curve that an increase in voltage is obtainable only with an increase in current and that if the current be held steady the voltage will not exceed a certain amount. Fig. 4, on the other hand, shows a characteristic voltage current curve which will be found to cause unstable operationin constant current series circuits. For suppose the device to be operating at the point marked 29, Fig. 4: While the voltage is coming up during the warming process from the lower voltage to this point there is an increase in voltage whenever there is an increase of current. But, a further increase in voltage will occur in case of a continued rise of temperature without an increase in current and even with an actual decrease of current. This means in the case of a serially operated mercury vapor apparatus that the vapor pressure rises so fast from the point 79 with increased temperature of the lamp that the voltage absorbed in the vapor and hencethe heat produced therein increases so rapidly as to maintain all radiation losses and support the actual vapor pressure with a lower current than would be suflicient to maintain the lower radiation losses at a somewhat lower temperature in the device and hence lower vapor pressure therein. When such lamps as those represented by the characteristic of Fig. 4 are operated in series on a constant current circuit trouble follows for if any one lamp is so constituted to run a little hotter or happens for any reason to get a little hotter than the others its vapor pressure will immediately rise rapidly and since the current is maintained by the generator its pressure and voltage goes up very rapidly until this device is injured or the series of lamps is extinguished.

Considering now Fig. 1, in which the individual mercury vapor devices 1, 1, 1, have a characteristic curve like that shown in Fig. 4, I show a method of constant current operation secured by the use of shunt circuits 2, 2, 2, which are automatically closed in shunt With the lamps 1, 1, 1, through the resistances, 3, 3, 3, by the thermostats, 4, 4, 4, or in one circuit by this thermostat whenever a lamp voltage tends to an excessive rise. The thermostat 4, when raised to a certain temperature by means of the elevation of temperature of the lamp to which it is adjacent, will lower the part 6 until the contact 5 closes the shunt 2. The'resistance 3 is so adjusted that the current then re maining in the lamp will drop slightly below the minimum danger current, thus persystem, in which the lamp 7 is adapted for use on alternating current. Shunts are closed through the resistances, 8, 8, by way of the cutouts, 9, 9, by the action of the magnets, 10, which are connected around the several lamps and thus measure the voltage thereon. The resistances, 11, 11, control the current in the magnets, 10, 1.0. The operation of this system is clear from that of Fig. 1, the chief difference being that in Fig. 2 the shunt circuit is closed by an electromagnet responsive to excess voltage on the lamp itself instead of by a thermostat. The currents through the resistances 8 are adjusted to abstract sufficient current from the lamp to prevent its overheating due to the full current flow, While the resistance 11 is adapted to control the magnetizing current of the coil 10. I

Fig.- 3 shows a lamp of the generaltype shown at 1 and 7 in Figs. 1 and 2, but modii fied to have a voltage current characteristic such that the voltage at a. critical point shall be increased only with considerable increase in current. In this lamp the lightgiving tube 12 is somewhat similar to those usually supplied with high pressure mercury vapor lamps while 13 is the cathode and 14 is the anode.' 15 is a condensing chamber,.16 an additional condensing chamber connected with 15 through the constriction 17. 18, 18 are mercury-sealed leadingin plugs for carrying the current to the mercury. As this lamp is shown for high pressure operation, it should preferably be constructed of quartz or some hard glass. If desired, I may use a return tube, 20, shown dotted, to carry condensed mercury from the auxiliary condensing chamber 16 to the electrode 14. The cooling chamber 19 may be attached to the cathode to absorb heat therefrom and assist in the maintaining of the normal mercury level in this electrode. The operation of the'chambers 16 and 15 is somewhat asfollows: When the device is started up cold, the vapor pressure in the light giving path is relatively low and a small weight of mercury vapor occupies a large volume. This vapor is con-, densed rapidly in the chamber 15. Since,

. however, a large excess of heat is generated in the low temperature condition of the device on account, of the relatively slow radiation into the air at such temperatures, the mercury rapidly heats up, thus increasing the vapor pressure very materially in the tube 12- and the chamber 15. A certain amount of mercury escapes through the throat 17 into the chamber 16 but in view where the amount of mercury escaping into' the chamber 17 becomes material so that this characteristic instead of being, as it would otherwise be, similar to that. shown in Fig. 4, it becomes more like that shown in Fig. 5.

While'I have shown some specific methods of gaining stability in these series circuits with containing evices having naturally straight upward characteristics, I do not wish to limit my invention to these pars ticularfeatures, for my invention is broader including the utilization of any specific means for correcting the tendency introduced by the use of constant current for individual devices to take abnormal temperatures orpressures. I do notwish to limit myself to mercury vapor apparatus, though my invention is especially adapted to this apparatus, nor do I wish to confine myself to a mercury electrode rather than one of some other appropriate material. Neither do I wish to limit myself to lamps operating in quartz tubes nor at the specific pressures here described. It is not necessary that the characteristic of such a lamp turn backward to the 'extentshown in the curve of Fig. 4; this figure, however, gives a good example of a device unstable on constant current.

I claim as my invention:

1. A mercury vapor apparatus comprising a container sealed and exhausted to a high degree of purity having a light-giving portion, a mercury electrode therein, a condensing chamber in communication with the vapor space of said apparatus, a second condensing chamber in communication with the interior of said lamp through a restricted opening adapted to pass a material A mercury vapor lamp comprising a I Signed at New York, in the county of light giving container and suitable elec- New York, and State of New York, this 9th 10 trodes therein including a supplementary day of September, A. D. 1912.

condensing chamber and a communicating passage thereto having anarea of opening PERCY THOMAS capable of passing suflicient vapor to oper- Witnesses:

ate said condensing chamber only under WM. H. CAPEL,

normal operating pressure in said lamp. THOS. H. BROWN. 

